| Title | Effects of aging and exercise training on eNOS uncoupling in skeletal muscle resistance arterioles. | | Author(s) | Sindler AL, Delp MD, Reyes R, Wu G, Muller-Delp JM | | Institution | West Virginia University; | | Source | J Physiol 2009 Jun 15. | | Abstract | Reduced availability of tetrahydrobiopterin (BH4) contributes to the age-related decline of nitric oxide (NO)-mediated vasodilation of soleus muscle arterioles. Depending on availability of substrate and/or necessary co-factors, endothelial nitric oxide synthase (eNOS) can generate NO and/or superoxide (O2-). We evaluated the effects of age and chronic exercise on flow-induced vasodilation and levels of NO and O2- in soleus muscle arterioles. Young (3 mo) and old (22 mo) male rats were exercise trained or remained sedentary (SED) for 10 wks. Flow-stimulated NO and O2-, as well as BH4 and L-arginine content, were determined in soleus muscle arterioles. Flow-induced vasodilation was assessed under control conditions and during the blockade of O2- and/or hydrogen peroxide. Exercise training enhanced flow-induced vasodilation in arterioles from young and old rats. Old age reduced, and exercise training restored, BH4 content and flow-stimulated NO availability. Flow-stimulated, eNOS-derived O2- levels were higher in arterioles from old SED compared to those from young SED rats. Exercise training increased flow-stimulated eNOS-derived O2- levels in arterioles from young but not old rats. O2- scavenging with Tempol reduced flow-induced vasodilation from all groups except young SED rats. Addition of catalase to Tempol-treated arterioles eliminated flow-induced vasodilation in arterioles from all groups. Catalase reduced flow-induced vasodilation from all groups. In Tempol-treated arterioles, flow-induced vasodilation was restored by deferoxamine, an iron chelator. These data indicate that uncoupling of eNOS contributes to the age-related decline in flow-induced vasodilation; however, reactive oxygen species are required for flow-induced vasodilation in soleus muscle arterioles from young and old rats. | | Language | ENG | | Pub Type(s) | JOURNAL ARTICLE
| | PubMed ID | 19528246 |
|
